Pipe scale analysis

Description

A calcium phosphate solid formed as an unintended consequence of a novel high-pH orthophosphate lead corrosion control strategy in Providence, RI, causing some consumer complaints and clogged plumbing. The calcium phosphate initially precipitated at orthophosphate doses above about 2 mg/L as PO4 during field testing, and the extent of precipitation increased with water age and higher temperature. Lab scale tests confirmed that doses above about 2 mg/L were required to form the precipitate in the absence of pre-existing calcium phosphate solids, and that the solid formed quickly at 60 °C (upper range for hot water heaters) and tended to dissolve at lower pH. Solubility modeling and other techniques suggest the solids are a mixture of compounds. For water systems currently practicing a high pH/low alkalinity corrosion control strategy, orthophosphate dosing can enhance plumbosolvency control without risky pH reduction, but calcium hardness puts a constraint on the maximum orthophosphate level that can be applied and tolerated. This dataset is associated with the following publication: Devine, C., K. Mello, M. Desantis, M. Schock, J. Tully, and M. Edwards. Calcium Phosphate Precipitation as an Unintended Consequence of Phosphate Dosing to High-pH Water. ENVIRONMENTAL ENGINEERING SCIENCE. Mary Ann Liebert, Inc., Larchmont, NY, USA, 41(5): 171-215, (2024).

Resources

Name Format Description Link
53 TIC%20RIPRFHP1_%201-13-2020.xlsx https://pasteur.epa.gov/uploads/10.23719/1528531/TIC%20RIPRFHP1_%201-13-2020.xlsx
53 RIPRFHP1_XRF%20data_2.25.19.xlsx https://pasteur.epa.gov/uploads/10.23719/1528531/RIPRFHP1_XRF%20data_2.25.19.xlsx
8 XRD%20data.csv https://pasteur.epa.gov/uploads/10.23719/1528531/XRD%20data.csv

Tags

  • calcium
  • orthophosphate
  • high-ph
  • solids-analysis

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